The field of this invention is heat and smoke vents for the roof of a building or other structure.
Heat and smoke vents such as disclosed in U.S. Pat. No. 3,731,442 and 3,461,607 are designed to be mounted in the roof of a building or other structure for transmitting light under normal conditions; and, in the event of a catastrophe such as a fire, the heat and smoke vents are designed to provide an exhaust opening for the passage of heat and smoke from the building. In U.S. Pat. No. 3,461,607 of Sandow, a heat and smoke vent is disclosed which includes a lifting means for lifting the cover of the heat and smoke vent upwardly in order to provide a heat escape opening. The lift mechanism in the Sandow U.S. Pat. No. 3,461,607 is actuated by a fusible link which releases the lifting mechanism to raise the cover after the receipt of a certain amount of heat. U.S. Pat. No. 3,788,013 of Veen, Jr. discloses a fire vent having a closure panel or partition which normally closes a tubular vent chamber or passage defined by an annular frame, with a support means for normally holding the closure in place, even against direct loading, but which collapses in response to the presence of heat, as from a fire, to drop the closure as well as certain support members out of the way to open up the tubular chamber and thus provide a vent. The support means includes a continuous rectangular upper support element which actually supports the closure or dome. A number of spaced lower supports are pivotally mounted on a cap portion and support the upper support element and thus the dome closure. The combination of the dome closure, the upper support member and the lower supports is not stable and will fall without further retention, which is provided by a cable which normally encircles a plurality of leverage arms attached to the lower supports. The cable has a heat sensitive link serially attached with it which, upon melting under heat, will release the cable and allow the lower supports, the upper support and the dome closure to fall downwardly.
Another type of heat and smoke vent uses a plastic cover which melts in response to certain temperature and heat conditions. The desirable aspect of this type of vent is that the cover is fully removed from the opening in order to allow for the escape of heat without obstruction from the raised framework and cover. However, the melt-type cover for a heat and smoke vent has disadvantages, also. The melt-type cover is generally considered to be very slow reacting because of the necessary passage of time before the entire cover melts sufficiently to soften enough to fall away. Further, for many types of melt-type covers, outside conditions such as extremely cold weather or rain may cause a cooling effect which neutralizes the rising heat from the fire in the building thereby preventing or delaying the melting of the cover and thus defeating the purpose of the entire unit. Another more inherent problem with any type of melt-type cover is that it cannot be quickly opened manually either from inside or outside; further, it cannot be used in conjunction with a smoke detector.